Around 400 BC a greek philosopher called Democritus proposed that if matter is repeatedly split we end up with particles so thinking that they cannot be split further.

• Democritus called the thinning particles Atomos from the greek word indivisible

Dalton’s atomic theory was able to explain the law of conservation of mass, law of constant composition and law of multiple proportion very successfully. However, it failed to explain the results of many experiments, for example, it was known that substances like glass or ebonite when rubbed with silk or fur generate electricity. Many different kinds of sub-atomic particles were discovered in the twentieth century. However, in this section we will talk about only two particles, namely electron and proton.